Journal
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY
Volume 137, Issue 659, Pages 1417-1430Publisher
WILEY-BLACKWELL
DOI: 10.1002/qj.853
Keywords
regional climate model; deep convection scheme; West African monsoon circulation; African easterly jet; African easterly waves
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The role of the representation of deep convection on key elements of the West African summer monsoon climate is addressed using the Regional Climate Model RegCM3. Two simulations in which a scheme of deep convection is activated and then turned off are performed and intercompared. Results show that the presence of deep convective heating along the intertropical convergence zone sustains increased lower-level baroclinicity favoring intensification of the jet core and leading to a more realistic African easterly jet. In addition, although the isentropic potential vorticity (IPV) is lower when the convection scheme is switched off, African easterly waves (AEWs) are still generated and propagate westwards but they dissipate around the west coast. Substantial differences between the two simulations occur mainly at the 6- to 9-day time-scale over land, when much weaker activity is simulated in the absence of convection. This indicates that orographic friction and low-level large-scale moisture convergence, generating high values of latent heat and IPV, may play the dominant role in the genesis and growth of AEWs and that deep convection acts to strengthen the overall wave activity and to favor their west coast development. Copyright (C) 2011 Royal Meteorological Society
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